Septic Tanks: Are they Anaerobic Digestors?

As we have been asked this question several times recently, we have added a page to our articles section on the www.anaerobic-digestion.com web site.

Septic Tanks: Are They Anaerobic Digestors?

As we have been asked this question several times recently, we have added a page to our articles section on the Anaerobic Digestion website.

Understanding Septic Tanks as Anaerobic Digestors

The short answer is yes, septic tanks do utilize the anaerobic digestion process for the partial treatment of sewage from isolated locations. These are areas where inhabited dwellings are located remote from public sewers, and a connection would otherwise be made to the sewer system.

However, it's important to note:

• Septic tanks provide only partial treatment and do not meet watercourse discharge standards.
• They are not commonly discussed as anaerobic digestors.
• Septic tanks are not typically recognized as significant methane emitters.

Methane Production in Septic Tanks

In my experience, I have rarely heard septic tanks mentioned as methane emitters. If methanogenesis does occur, it is likely at low temperatures, which is less efficient for methane-producing bacteria (methanogens) to thrive.

However, in hotter climates, methane gas can be produced very effectively from domestic effluent type anaerobic digestors and used for cooking and other purposes. Such installations are widespread in countries like China and India.

Comparison of Anaerobic Digestors

Characteristic	Septic Tanks	Anaerobic Digestors
Primary Use	Partial sewage treatment	Complete organic waste treatment
Common Locations	Remote inhabited areas	Both urban and rural areas
Methane Production	Minimal	High (especially in warm climates)
End Use of Biogas	Not typically utilized	Cooking, heating, electricity

Should We Collect Methane from Septic Tanks in the West?

The idea of collecting methane from septic tanks in Western countries is intriguing. Given the environmental benefits of reducing methane emissions, it might be worth exploring whether septic tanks can be optimized for methane capture and utilization.

We always appreciate feedback and comments from our readers. Your insights on this topic would be particularly valuable, so please share your thoughts!